The opposite of a hipster. Whereas a hipster starts trends before they become mainstream, a negahipster destroys trends, making them unpopular. With the trend driven back underground, the hipster is once again given free reign over the now retro trend until its inevitable return to the populus.

Chris: "Dude, what are you doing wearing that sleeping mask? Don't you know those have gone mainstream?"
Erica: "Actually, that negahipster Shadi was seen wearing a sleeping mask during third period French class, so no one wants to wear them anymore."
Chris: "God bless him."